Publication Date:
2021-05-19
Description:
In this research, size selectivity for narrow-barred Spanish mackerel (Scomberomorus commerson) and other
species such as Indo-Pacific king mackerel (Scomberomorus guttatus), Longtail tuna (Thunnus
tonggol),Kawakawa (Euthynnus affinis), Talang queenfish (Scomberoides commersonnianus) and John's snapper
(Lutjanus johnii) were investigated in mesh sizes of surface, mid-water and bottom drift nets in coastal waters of
Bandar Abbas and in the western part of Hormozgan province (fishing ports of Gong and Bustaneh), as well as
of catch composition from the fisheries. The data required for the relevant analysis was collected for the years
2012-2014.
In order to determine the size selectivity of the investigated species, cumulative probability distributions of
retention girth (operculum and maximum girth) at length was used. The results indicated that there is a linear
relationship between length (fork length or total length) and transvers morphometric parameters in six positions
of girth at fish species. Seven types of gillnets with stretched mesh sizes of 70, 76, 79, 101, 114, 132 and 165
mm and different technical characteristics were investigated for size selectivity of S. commerson, in which the
optimal length were 38, 44, 49, 63, 74, 86 and 100 cm FL in the respective meshes. The capture processes of S.
commerson was mostly in wedging in the all mesh sizes, whereas in the other species, depending on the
morphology of fish, the retention method was different. The comparison of length frequency distribution of
kingfish with mean length at maturity (Lm50%) indicated that, depending on mesh size, the frequency of the
immature fish in the catch was between 4 and 100%. On the basis of optimal length at mesh size, the minimum
legal mesh size of kingfish was estimated as 162 mm. Size selectivity curve was also represented for other
species, which depending on fish morphology the model was inadequate in fitting the data. The results from the
catch composition showed that the species diversity is different by fishing method. In mesh sizes of 70, 76 and
79 mm, the kingfish was captured in target and bycatch species depending on time by the surface drift gillnet
fishery operated by the fishing boats. In this type of gillnet fishery, bycatch accounted for more than half of the
total catch in which some of the species was important economically. Catch composition in gillnet fishery
operated by dhows was different depending on fishing method. At the first step, it is necessary to impose a ban
on gillnets with mesh sizes of 70, 76 and 79 mm in second half of the year. In the next step, for establishing the
regulation on minimum legal mesh size of kingfish, it needs to do further study in seas trails aimed at determine
the appropriate mesh size. Also, in the multispecies fishery, it is necessary to do a research for optimization of
mesh sizes of gillnets and to implement minimum legal mesh size for the main target species.
Description:
Iranian Fisheries Science Research Institute
Description:
Published
Keywords:
Size selectivity
;
Narrow-barred Spanish mackerel
;
Optimal length
;
Morphometric
;
Parameters
;
Bycatch
;
Scomberomorus commerson
;
Gillnet
Repository Name:
AquaDocs
Type:
Report
,
Refereed
Format:
112pp.
Permalink
